The invention relates to a device for reducing drive line vibrations excited at the engine, in particular a split flywheel, having two device or flywheel elements which are arranged mutually on the same axis and are coupled to one another in a driven manner by means of a spring mounting. One of the device or flywheel elements is connected to the engine and the other is connected to the transmission (or drive) line. A frictional clutch which is affected by clearance is positioned between the device or flywheel elements.
A corresponding device which is integrated into a clutch connected between the engine and transmission is the subject matter of the German Offenlegungsschrift No. 2,814,059. Moreover, a correspondingly developed, split flywheel is described in the earlier German Patent Application No. P 34 30 457.6-13 which corresponds to U.S. Pat. No. 4,662,239.
In these known devices, the spring mounting and/or the frictional clutch between the device or flywheel elements are of a relatively rigid design. The stops are arranged for limiting the relative rotation between the device or flywheel parts. Without such a rigid design, there would be the risk of stops colliding with one another, creating noise and shocks in the drive line. Because of the rigid spring mounting, flywheel elements having relatively large masses or moments of inertia must be arranged in the split flywheel. This is because in order to permit a so-called hypercritical state during travel operation, the resonant frequency must be very low and be below the frequency of the vibrations occurring during idling operation. That is, the frequency of the vibrations excited by the engine is clearly above the resonant frequency of the split flywheel. Consequently, the possibility exists that if the clearance of the frictional clutch is of an appropriate size, practically only the spring mounting is active between the flywheel elements during travel operations, and accordingly it is practically impossible for the high frequency vibrations excited by the engine and measured at the resonant frequency of the split flywheel to be transmitted to the rest of the drive line. On the other hand, if it is unavoidable that the resonant range of the flywheel has to be run through when the engine is being started, greater relative rotation of the flywheel parts relative to one another will be damped by the active, frictional clutch. However, the friction contact must become active with a minimum damping force which, as a sudden rise in the torque transmitted between the flywheel elements, leads to a certain discomfort in certain operating conditions.
It is therefore the object of the invention to create a device for reducing drive line vibrations excited at the engine, in particular a split flywheel, in such a way that comfort is clearly increased, especially in the critical ranges, such as partial-load travelling ranges.
To achieve this objective, it is provided according to preferred embodiments of the invention that the abutment of the spring mounting, which abutment is allocated to one device or flywheel element, is arranged on an abutment part which is frictionally connected to this device or flywheel element in a driven manner without limitation of the rotating capacity of the flywheel elements relative to one another, with the force of the frictional contact being greater than the maximum torque of the engine.
The invention is therefore based on the general idea that the strength of the spring mounting between the device or flywheel elements and also the clearance of the frictional clutch preferably arranged between these elements can be apportioned exclusively with regard to a maximum comfort if the device or fly-wheel elements can be rotated relative to one another to any extent. Therefore, considerable relative movements of these elements with respect to one another which could possibly occur in the resonant range can be reduced over a considerable range. At the same time, it is particularly advantageous that this reduction, which takes place against the damping resistance of the friction contact by the relative movement between the abutment member and one device or flywheel element frictionally coupled to it, can come into action smoothly, because even the strength of this resistance can be apportioned exclusively with regard to comfort.
According to preferred embodiments of the invention, the spring mounting is subdivided into at least two spring mounting groups which are connected to one another via an intermediate member which can rotate in spring-like manner relative to the two device or flywheel elements, with the frictional clutch affected by clearance being arranged parallel to at least one spring mounting group between the intermediate member and one of the device or flywheel elements. In this arrangement, the spring mounting can be arranged with a large displacement and corresponding elasticity. At the same time, it is favorable with respect to comfort if the frictional clutch affected by clearance is only arranged parallel to one spring mounting group.
Moreover, it is expedient according to certain preferred embodiments to arrange several frictional clutches having different clearances in parallel connection to enable a progressive increase in friction contact and in the damping connected with the latter during greater relative movements of the device or flywheel elements to one another.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.